Various elastomers such as ethylene-propylene diene terpolymer (EPDM) and styrene-butadiene copolymer have been utilized for many years in applications requiring a sealing contact between the elastomer and another object, such as in glass run channels which are positioned in the window frames of automobile doors to provide a seal between the window frame and the glass.
The elastomer utilized in glass run channel applications generally possesses excellent weatherability properties and is flexible to provide a seal of the elastomer against the window glass without the application of excessive force. Nevertheless, most suitable flexible elastomers lack the low-friction, abrasion or wear resistant properties necessary for ease of travel of window glass within the glass run channel and for long life of the glass run channel.
Accordingly, an accepted practice to provide durability and abrasion resistance to the elastomer forming the glass run channel has been to provide a flocking layer to the contact surface between the elastomer and the glass surface. However, application of the flocking layer about a corner of the glass run channel requires a flock adhesive containing volatile organic compounds and the problems associated therewith and requires a complicated and costly manual application of flocking.
One alternative to flocking of a glass run channel for improved abrasion and wear resistance is a coating such as described in U.S. Pat. Nos. 5,115,007 and 5,221,707. However, a coating as described in U.S. Pat. Nos. 5,115,007 and 5,221,707 typically includes a solvent of a volatile organic compound which necessitates careful handling and manufacturing procedures.
Glass run channels have also included a combination of a thermoplastic wear strip, for example polypropylene, that is adhered to the EPDM across the bottom of the glass run channel and flocking material that is adhered to the EPDM at the lips of the glass run channel. Although polypropylene possesses the required low friction, high abrasion resistance and high durability properties, a polypropylene wear strip is excessively rigid and must be more than 1 mm thick to provide acceptable wear performance. In addition, polypropylene wear strips have been found to melt and flow thereby generating nonuniform rough sections at the corners and spliced areas when molded with an EPDM substrate at elevated temperatures of about 350 degrees fahrenheit.
It will be appreciated that a rubber molding process is typically too hot to utilize thermoplastic films. The temperature of the mold cavities and mold core inserts must be kept high, for example 350 degrees fahrenheit or more, to cure the rubber compound. In addition, the rubber compound temperature must also be maintained low enough to prevent cure of the rubber compound before the rubber compound flows into the mold cavity. As a result, thermoplastic films typically melt on the mold cavity surfaces such that the films do not transfer to the rubber compound substrate as a smooth uniform continuous thin film.
In view of the foregoing, it is recognized that there is a significant need for an improved method of manufacturing glass run channel composites, particularly, corner glass run channel composites that overcomes the problems of the prior art. As described herein, in contrast to heretofore known methods of off-line flocking and/or coating of a glass run channel corner or on-line flocking and/or coating of a glass run channel, the present invention provides the advantages of 1) a glass run channel composite having improved performance, e.g., low friction and extremely high abrasion resistance, 2) eliminating volatile organic compounds typically present in a coating, 3) simplifying production, i.e., no coating thickness control, cure process requirements, or labor intensive procedures, 4) application of a uniform continuous film to areas previously unsuited for coating or flocking because of certain geometrical restrictions, 5) a film top surface flush with the surrounding top surface of the glass run channel substrate to provide an aesthetically pleasing appearance and a composite that is not prone to peeling or delamination, and 6) a continuous length of glass run channel having little or no seam lines when formed by joining two or more glass run channels having thin films of ultra high molecular weight polyethylene.